If Lindsey Graham has to change cellphone numbers, he has Donald Trump to thank.

On Tuesday, Trump ramped up his attacks on the South Carolina senator — who made headlines Monday for calling the Donald a “jackass” — and even gave out Graham’s private phone number.

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Trump began his rambling diatribe by calling Graham a “lightweight” and an “idiot.”

“He doesn’t seem like a very bright guy. He actually probably seems to me not as bright as Rick Perry. I think Rick Perry probably is smarter than Lindsey Graham,” Trump added, riffing on prior insults he had lobbed at the former Texas governor.

Then Trump transitioned to an embarrassing anecdote, which the billionaire real estate developer said was from a few years ago, in which Graham called Trump “begging” him for a good reference with Trump’s pals on the Fox News morning program “Fox & Friends.”

Trump said that he promised Graham he would put out a good word, and the South Carolina Republican then gave him his phone number to follow up.

Trump then read out what he said was Graham’s phone number, telling his supporters to “try it.”

“I wonder what caused that,” Graham told a POLITICO reporter who dialed the number, about the influx of calls.

The feud between Graham and Trump has escalated in recent days, especially as the South Carolina Republican has ripped into Trump for saying that Graham’s good friend, Sen. John McCain (R-Ariz.), is not a war hero because he was captured.

On Monday evening, Graham told CNN that Trump was “becoming a jackass.”

By Tuesday, Graham was appearing on “CBS This Morning” and calling Trump “the world’s biggest jackass.” Even “the jackasses are offended” by Trump’s remarks, Graham added.

Asked whether he thinks Trump can sustain his place at the top of Republican presidential primary polls, Graham — who is also seeking the nomination — said no.

“I think the beginning of the end has come. The beginning of the end has arrived because he’s crossed a line with the American people that will not be tolerated.”

Later on the program, host Gayle King asked whether Graham had called Trump to ask him to cut it out.

“What good would that do, calling Donald Trump?” Graham said. “I’m more worried about the Iran nuclear deal than I am Donald Trump, and so is John McCain.”

McCain reacted with a laugh when asked about Trump’s latest action.

“I was wondering if Donald Trump has mine,” McCain told POLITICO. “Seems like it’s kind of a crazy time, doesn’t it?”

Later in the afternoon, Graham solicited his followers’ advice on whether he should get an Android or iPhone as his new phone.